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otoiser — open transactions on independent scientific-engineering research 

FUNKTECHNIKPLUS # JOURNAL 

Theorie — Experimentation — Metrologie — Logiciel — Applications 
ISSUE 5 - TUESDAY 30 SEPTEMBER 2014 - YEAR 2 



1 Contents 

2 About 

3 Editorial Board - Technical Support 

4 Information for Peers - Guiding Principles 

# Electrical Engineering - Experimentation 

7 Electrical Machine Insulation: Traditional Insulating 
Materials, Nanocomposite Polymers and the Question of 
Electrical Trees 

M. G. Danikas, R. Sarathi 

# Telecommunications Engineering - Logiciel 

33 Antenna Radiation Patterns: RadPat4W - FLOSS for MS 
Windows or Wine Linux 

N. I. Yannopoulou, P.E. Zimourtopoulos 




el-l 



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FUNKTECHNIKPLUS # JOURNAL 



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ISSUE 4 - YEAR 2 



About 



Editorial Board 

# Electrical Engineering 

# High Voltage Engineering # Insulating Materials 
Professor Michael Danikas 

EECE, Democritus University of Thrace, mdanikas@ee.duth.gr 

# Electrical Machines and Drives # Renewable Energies 

# Electric Vehicles 

Assistant Professor Athanasios Karlis 

EECE, Democritus University of Thrace, akarlis@ee.duth.gr 

# Computer Engineering # Software Engineering 

# Cyber Security 

Associate Professor Vasileios Katos 

EECE, Democritus University of Thrace, vkatos@ee.duth.gr 

# Internet Engineering # Computer Science 

# Simulation # Applied Education # Learning Management Systems 
Lecturer Sotirios Kontogiannis 

BA, TE Institute of Western Macedonia, skontog@gmail.com 

# Hypercomputation # Fuzzy Computation # Digital Typography 
Dr. Apostolos Syropoulos, Xanthi, Greece 

BSc-Physics, MSc-, PhD-Comp. Science, asyropoulos@yahoo.com 

# Applied Mathematics # Functional and Numerical Analysis 

# Applied Electromagnetics # Control Theory 
Dr. Nikolaos Berketis, Athens, Greece 

BSc-Math, MSc-Appl . Math, PhD-Appl . Math, nberketis@gmail.com 

# Telecommunications Engineering 

# Applied Electromagnetics # Metrology # Applied Education 

# Simulation # Virtual Reality # Amateur Radio # FLOSS 

# Applied Physics # Electronics Engineering 

Dr. Nikolitsa Yannopoulou, Scheiblingkirchen, Austria 
Diploma Eng-EE, MEng-EECE, PhD-EECE, yin@arg . op4 . eu 

Dr. Petros Zimourtopoulos, Scheiblingkirchen, Austria 
BSc-Physics, MSc-Electronics-Radio, PhD-EE, pez@arg . op4 . eu 

Technical Support 

Konstantinos Kondylis, Doha, Qatar 

Diploma Eng-EECE, MEng-EECE, kkondylis@gmail.com 

Christos Koutsos, Bratislava, Slovakia 
Diploma Eng-EECE, MEng-EECE, ckoutsos@gmail.com 



SATURDAY 31 MAY 2014 



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FUNKTECHNIKPLUS # JOURNAL 




About 



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FUNKTECHNIKPLUS # JOURNAL 



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ISSUE 4 - YEAR 2 




About 



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FUNKTECHNIKPLUS # JOURNAL 




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ISSUE 4 - YEAR 2 



ELECTRICAL ENGINEERING 



EXPERIMENTATION 



Electrical Machine Insulation: Traditional 
Insulating Materials, Nanocomposite Polymers 
and the Question of Electrical Trees 

M.G. Danikas, R. Sarathi * 

Power Systems Laboratory, Department of Electrical and 
Computer Engineering, Democritus University of Thrace, 

Xanthi, Greece [l] 

Department of Electrical Engineering, 

Indian Institute of Technology Madras, Chennai, India [2] 

Abstract 



Electrical machine insulation consists basically of epoxy 
resin and mica foils. Both are good insulating materials and 
they proved to withstand large partial discharges and/or the 
combined attack from electrical, thermal and mechanical 
stresses. Nowadays alternatives to the traditional insula- 
ting materials exist, namely those of nanocomposite poly- 
mers, which present somehow improved performance regarding 
the aforementioned stresses. It is the aim of the present 
paper to investigate mechanisms of electrical treeing and/or 
breakdown in machine insulation as well as to study possible 
improvements with the aid of nanocomposite polymers. 



Keywords 

Machine insulation, nanocomposite polymers, breakdown, par- 
tial discharges, breakdown strength, pre-breakdown phenomena 



Introduction 

Machine insulation is ge- 
nerally characterized by hard 
materials, capable to with- 
stand partial discharges of 
quite large magnitudes. An 
electrical insulation in high 
voltage machines must have a 
high breakdown strength, a 
good long term functioning 
without possible problems em- 



anating from degradation ef- 
fects (partial discharges 
(PD), treeing phenomena etc.) 
and certainly rather small - 
if any - leakage currents. 
Such insulation must also ha- 
ve a satisfactory thermal per- 
formance and must withstand 
relatively high temperatures. 
The electrical and thermal 
properties of such insulation 



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M.G. DANIKAS, R. SARATHI 



must not be deteriorated be- 
cause of some extreme condi- 
tions, i.e. the highest pos- 
sible temperature to be tol- 
erated should not provoke any 
alterations to the insulation 
itself. The electrical machi- 
ne insulation should have good 
long term functioning and it 
should present only small 
changes (to be tolerated) af- 
ter many thermal cycles. Mo- 
reover, electrical machine in- 
sulation should have a satis- 
factory mechanical behavior, 
i.e. high mechanical strength 
which should stay high even 
at higher temperatures. 

Thermal stressing may cau- 
se some sort of breakdown on 
the surface of mica sheets, 
whereas mechanical stressing 
may cause also fissures in 
epoxy resin and in mica. Elec- 
trical stressing may cause 
partial discharging in possi- 
ble existing imperfections of 
the insulation and thus lead 
to electrical failure [1] . 
Needless to say that all pro- 
perties - electrical, mechan- 
ical and thermal - are vital 
for the reliable operation of 
rotating machines. The insu- 
lation should have satisfac- 
tory electrical properties, 
it should withstand the ex- 
pansion and contraction dur- 
ing temperature cycles and it 
should respond in a good way 
to mechanical stresses. 

Rotating machines can be 
divided into two categories: 



those with voltage ratings 
less than 6.6 kV and those 
with voltage ratings higher 
than 6.6 kV. Mica has been 
used for years in the elec- 
trical machine industry. Mica 
sheets with a backing of 
glass cloth and of binding 
material, like epoxy resin, 
have been the classical insu- 
lation systems for rotating 
machines. Generally speaking, 
such insulating systems have 
proved to be reliable [2]- 

[4] ■ 

Research on possible break- 
down mechanisms in such sys- 
tems revealed that PD and 
electrical treeing may lead 
to breakdown [5]. As is poin- 
ted out in published work, 
electrical trees propagate 
through the weaker material 
and they tend to reach the 
opposite electrode, resulting 
thus in total failure [2]- 

[5] , 

It is the aim of the pre- 
sent paper to explore mecha- 
nisms of failure both in con- 
ventional insulating materi- 
als used for rotating machi- 
nes as well as to investigate 
alternative insulating sys- 
tems based on a new series of 
insulating materials, namely, 
the nanocomposite polymers. 
Simulation data will be pre- 
sented for conventional insu- 
lating materials and possible 
improvements will be sugge- 
sted. It has to be noted that 
this review is by no means an 



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ISSUE 5 - YEAR 2 




ELECTRICAL MACHINE INSULATION: TRADITIONAL INSULATING MATERIALS 



exhaustive one. Rotating ma- 
chine insulation is a complex 
insulating system and, in the 
context of the present paper, 
only some aspects of it will 
be treated. It should also be 
added that the present review 
does not deal with the sub- 
ject of enameled wiring, 
which will possibly consist 
the topic of another review 
paper . 

At this stage, it would be 
fitting to state that review 
papers are useful even today. 
Why? Because they give some 
insight to the newcomer as 
well as to the experienced 
scientist regarding a partic- 
ular subject. Although we are 
flooded with much information 
from the Internet with prac- 
tically thousands and thou- 
sands of references (books, 
papers, journals etc.), a re- 
view paper can always be a 
starting point for the inter- 
ested person. The purpose of 
a review paper is not simply 
to collect information on a 
particular subject, it is ra- 
ther to offer - besides a 
wealth of information and the 
relevant references - com- 
ments and interrelations be- 
tween experimental data, cri- 
ticism and approaches for pos- 
sible new theoretical models, 
it is probably the right pla- 
ce to also propose some new 
insights from the reviewer, 
it is the place to offer some 
thoughts for possibly new de- 



velopments. This is why we be- 
lieve in the validity of such 
efforts, this is why we think 
that reviews will always be 
useful, despite the flood of 
new scientific and technical 
information, almost on an eve- 
ry second-basis. 

Conventional Insulating 

Materials for Rotating 

Machines 

Mica sheets are used in 
rotating machine insulation 
as traditional insulating ma- 
terial. Mica is a natural mi- 
neral. Its crystalline nature 
gives very strong bonds in 
one plane and very weak Van- 
der-Waals's forces in the pla- 
ne normal to this. The conse- 
quence of that is that mica 
can be split easily into fla- 
kes [2] . Mica has excellent 
tracking strength, high break- 
down field strength, very good 
resistance to PD, high volume 
resistance as well as good 
thermal stability up to 6000 
C [2]. For high voltage ap- 
plications, mica sheets use 
as bonding material epoxy re- 
sin, a thermosetting material 
with very good electrical 
properties and good resis- 
tance to PD. Moreover, for a 
resin to be suitable for long- 
term operation, it requires 
high thermal stability with 
low electrical loss at ser- 
vice temperature and at power 
frequency, excellent adhesion 
to mica, high resistance to 



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FUNKTECHNIKPLUS # JOURNAL 




M.G. DANIKAS, R. SARATHI 



moisture, chemicals and other 
contaminants, high mechanical 
strength over a range of ser- 
vice temperatures, dimensio- 
nal stability, ability to ope- 
rate at higher temperatures 
and a short cure time at 1500 
C to 1600 C [6] . In typical 
rotating machine insulations, 
mica sheets form a sort of 
sandwich with epoxy resin, 
thus rendering the electrical 
breakdown of such a combined 
system rather difficult [7] . 

One of the problems facing 
the mica/epoxy resin insula- 
tion is the one of electrical 
trees, which may grow and 
eventually bridge the gap be- 
tween the electrodes causing 
thus ultimate failure. Elon- 
gation of electrical trees 
has been experimentally ob- 
served in [8], [9]. In such a 
case, the mica sheets consist 
the harder material and the 
electrical trees propagate 
via the epoxy resin, which is 
the weaker material. Electri- 
cal trees propagate, gener- 
ally speaking, more easily in 
epoxy resin, a fact also con- 
firmed in another paper [10] . 

Normally prior to electri- 
cal treeing, PD take place in 
defects in the machine insu- 
lation. Such defects may come 
about from construction or 
from the stressing of the in- 
sulation. As said, the stres- 
sing in machine insulation 
can be multi-factor stress- 
ing, i.e. the insulation may 



be stressed because of high 
voltage, thermal cycles as 
well as from mechanical load- 
ing [11] . Defects can come 
about as enclosed cavities, 
delaminations, problematic 
interfaces, possible enclosed 
foreign particles etc. The 
consequence of all these is 
local electric field enhance- 
ment, PD activity which sub- 
sequently may result to insu- 
lation damage. Such PD can be 
quite intense in the order of 
1-10 nC [12], [13]. These phe- 
nomena can have a cumulative 
effect and cause aging and 
shortening of the lifetime of 
machine insulation [14], [15]. 

Rotating machine insula- 
tion systems suffer from what 
most of composite insulating 
systems suffer, i.e. the pre- 
sence of interfaces. Mica 
sheets and epoxy resin con- 
sist of a system with multi- 
ple interfaces. Interfaces 
may encourage electric field 
intensifications in the wea- 
ker material and, thus, the 
cause of deteriorating phe- 
nomena. On the other hand, 
thinner (and consequently mo- 
re) mica sheets may delay the 
discharge process in that 
discharges lose energy at the 
interfaces, i.e. a discharge 
having penetrated one layer 
could not enter the next 
layer of material until the 
spot on the interface, cen- 
tred on the channel, had been 
charged to a potential which 



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ISSUE 5 - YEAR 2 




ELECTRICAL MACHINE INSULATION: TRADITIONAL INSULATING MATERIALS 



could produce a field compa- 
rable with that of the chan- 
nel at the level in question 
[16]- 

Breakdown mechanisms in- 
side the insulation may start 
from defects due to excessive 
electrical field. Previous 
work done on epoxy resin sam- 
ples showed that it is possi- 
ble that trees emanate from 
enclosed cavities, causing 
thus conditions for further 
propagation and eventual fai- 
lure [17] . Although such ema- 
nating trees are still put 
into question from some re- 
searchers [18], experimental 
evidence can hardly be re- 
futed. PD cause pits on the 
inner surface of such cavi- 
ties possible and then elec- 
trical trees may ensue. One 
aspect that should be stres- 
sed is that of the applied 
voltage: for meaningful com- 
parisons of data (perhaps with 
several years interval) and/ 
or comparison of data in the 
same laboratory or factory, 
it is essential to use iden- 
tical wave shapes of volta- 
ges [19] . It is something 
that people tend to forget 
but something that comes out 
when PD measurements - com- 
parisons of such measurements 
at different times - have to 
be performed. 

Mica barriers delay tree 
propagation. Depending on the 
dielectric constants of mica 
sheets and of epoxy resin as 



well as on the threshold vol- 
tages, electrical trees may 
take different forms but, in 
general, they seem not to pe- 
netrate the mica barriers 
[20]. Mica barriers may re- 
sult in a major increase in 
breakdown time, this increase 
being depended on both the 
tree growth time and the set- 
in of the failure time [21] . 

The interplay and interde- 
pendence between PD and elec- 
trical treeing has been shown 
before, where in narrow holes 
of short length small PD in a 
rather high number may be pro- 
duced whereas in holes of lar- 
ger diameter and longer length, 
fewer PD but with larger mag- 
nitudes will ensue [22] . In any 
case, trees tend to grow a- 
round the mica barriers [23] . 

A crucial factor determin- 
ing tree propagation along a 
mica barrier is the type of 
chemical bonding between mica 
and epoxy resin. The stronger 
the bonding, the higher the 
resistance to the tree propa- 
gation [24] . Imperfections 
may result from imperfect mi- 
ca sheet overlapping, from 
the creation of cavities in 
parts which are at the edges 
of windings, from not so 
smooth mica sheets or from 
abrupt interruptions of mica 
sheets (because of construc- 
tional faults) [25]. Further- 
more, the layered mica can 
delaminate under thermo-mecha- 
nical stresses and thus cause 



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FUNKTECHNIKPLUS # JOURNAL 




M.G. DANIKAS, R. SARATHI 



cavities, which in turn will 
lead to PD [25] . Examples of 
imperfections are given be- 
low. In Fig. 1, a winding in- 
sulation is shown and the 
different radii of mica sheets 
are noted. In Fig. 2, imper- 
fections in winding insula- 
tion are noted. 

Experimental evidence that 
a mica barrier may withstand 
electrical treeing much bet- 
ter than epoxy resin was gi- 
ven in [10], where it was al- 
so noted that the breakdown 
strength of such a combina- 
tion depends on the thickness 
of mica sheets, on the thick- 
ness of epoxy resin, the tem- 
perature, the type of epoxy 
resin as well as the cleanli- 
ness of both materials. 

Generally speaking, the 
time to breakdown is the sum 
of the time from the initial 
PD activity and the creation 
of initial tree channels and 
the growth time of trees to 
the final breakdown. For some 
authors, there is an incuba- 
tion period during which PD 
activity is barely detectable 
and trees grow only slightly, 
then a period of tree expan- 
sion follows and finally a wi- 
dening of the smaller tree 
channels which eventually 
leads to bridging of the elec- 
trodes and the breakdown [9] . 
For others, two stages of tree- 
ing are observed: first, the 
inception period which may be 
for very many cycles, follo- 



wed by a relatively short pe- 
riod of tree growth. PD de- 
tection reveals that a tran- 
sition is accompanied by big 
increase in the PD magnitude, 
which persists until break- 
down [26] . A good account of 
PD measurements and the ef- 
fect of PD in rotating ma- 
chines were given in [27], 
where examples of "good" 
(i.e. relatively free of PD) 
and "bad" (with delamina- 
tions) windings were presen- 
ted. In [27], it was empha- 
sized that for any comparison 
between PD measurements, the 
experimental conditions play 
a predominant role, a state- 
ment that echoes reference 
[19] . Certainly, a condition 
assessment of windings can be 
done by continuously monitor- 
ing the PD activity, taking 
into account that an increase 
in discharge activity occurs 
when the insulation is eroded 
and also that a PD activity 
can manifest itself both as 
internal PD activity and as 
surface discharges [28] . A 
good account of the relation 
between PD and tree structu- 
res was given in [29], where 
it was emphasized that elec- 
tron avalanches, field fluc- 
tuations arising from the 
discharges themselves, local 
variations in permittivity and 
resistance of the insulation 
can play a decisive role for 
the electrical tree propaga- 
tion. Minor variations of 
trapped space charges may 



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ISSUE 5 - YEAR 2 




ELECTRICAL MACHINE INSULATION: TRADITIONAL INSULATING MATERIALS 

lead to preferred directions tions and, thus, may also af- 
for new tree channel forma- feet the tree propagation. 




Fig. 1: Winding insulation. Note the different radii which 
cause the different bending of mica sheets (after [10]) 




Fig. 2: Imperfections of winding insulation at the edges 

(after [10]) 



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FUNKTECHNIKPLUS # JOURNAL 



M.G. DANIKAS, R. SARATHI 



It is not to underestimate 
that several years ago, prob- 
lems with very small PD - not 
to say with phenomena below 
the inception voltage - were 
noticed in turbine generator 
armature winding insulations, 
namely that although such win- 
dings withstood standard test- 
ing, they failed short after 
the beginning of their ser- 
vice. Why was that? Possibly 
because extremely small PD, 
not easily detected by con- 
ventional methods, are at 
work and little by little 
could deteriorate the insula- 
tion of such windings [30] . 

Mica sheets offer a good 
protection to breakdown paths 
and/or to electrical treeing. 
This certainly depends on the 
applied voltage. Simulations 
in epoxy resin/mica sheets 
show that there is a voltage 
limit beyond which breakdown 
even of mica sheets is possi- 
ble. From a certain voltage 
value upwards, mica sheets 
are also prone to treeing, as 
the following figures show. 
In Fig. 3, the applied volt- 
age is 28 kV, which creates a 
rather distinguished form of 
treeing in the epoxy resin 
but which cannot penetrate the 
mica sheet. On the contrary, 
in Fig. 4, with another 
higher applied voltage, the 
mica sheet is penetrated by 
the electrical trees and in 
Fig. 5, there is a complete 
failure of the system epoxy 



resin/mica sheet. It is to be 
noted that in Fig. 4 as well 
as in Fig. 5, the trees in 
the epoxy resin are of bush- 
type and in the mica sheet of 
branch-type. This is because 
trees in the weaker material 
are far more numerous and 
thus they are interconnected 
much more densely than in the 
stronger material. The simu- 
lations shown in Figs. 3, 4 
and 5 were performed with the 
method of Cellular Automat 
[31] -[33]. The different ty- 
pes of electrical trees in 
epoxy resin (bush-type) and in 
mica sheet (branch- type) de- 
pend on the applied voltage 
as well as on the type of the 
insulating material [34] . In 
Figs. 4 and 5, the progres- 
sion of treeing towards the 
opposite electrode can well 
be seen. It is indeed a ques- 
tion of time before the tree- 
ing structure reaches the op- 
posite electrode. 

All in all we observe that 
conventional insulating mate- 
rials functioned more or less 
satisfactorily. Both experi- 
ments and simulations indi- 
cated that breakdown paths 
follow the easiest way to the 
other electrode, i.e. through 
the epoxy resin, which is the 
weaker of the two materials. 
Breakdown of the mica sheets 
may be possible but this de- 
pends on their thickness as 
well as on the voltage ap- 
plied . 



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ELECTRICAL MACHINE INSULATION: TRADITIONAL INSULATING MATERIALS 




Fig. 3: Propagation of electrical tree in epoxy resin and mica 
sheet. Applied voltage 28 kV, breakdown strength of epoxy re- 
sin is 26 kV/mm, breakdown strength of mica sheet is 35 kV/mm 




Fig. 4: Propagation of electrical tree in epoxy resin and mica 
sheet. Applied voltage 34 kV, breakdown strength of epoxy re- 
sin is 26 kV/mm, breakdown strength of mica sheet is 35 kV/mm 



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M.G. DANIKAS, R. SARATHI 




Fig. 5: Propagation of electrical tree in epoxy resin and mica 
sheet. Applied voltage 34 kV, breakdown strength of epoxy re- 
sin is 26 kV/mm, breakdown strength of mica sheet is 35 kV/mm 



Is there a way to improve 
even more the electrical per- 
formance of such a composite 
system? The following section 
will concentrate on some of 
the modern materials proposed 
for machine insulation. 

(As an explanatory note to 
this paper: It is evident 
from the present review that 
here we are not interested in 
an estimation of lifetime ex- 
pectancies of the insulation 
in connection with the qual- 
ity of the insulation itself. 
Models of lifetime expectan- 
cies have been developed and 
commented upon elsewhere [35] . 
It should also be emphasized 
that, the present paper is not 
concerned with the technica- 
lities of the measurements of 
PD in rotating machine insu- 



lation either [36] ) . 

Nanocomposite Polymers for 

Rotating Machine Insulation 

A recent paper on nanodi- 
electrics applications has 
pointed out that "three types 
of insulations have been de- 
veloped with great improve- 
ments in the resistance to 
partial discharges: first in 
random-wound wire enamel; se- 
cond in form-wound strand 
enamel; and third in form- 
wound stator bar insulation 
or ground wall insulation" 
[37] . Of these aforementioned 
applications, the one that 
interests us most for the 
time being is the third one, 
i.e. that of stator bar insu- 
lation. The other two types 
of insulation may constitute 



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the subject of yet another 
review paper. In the context 
of the present paper, we will 
concentrate on some off the 
novel insulating materials 
concerning the stator bar in- 
sulation . 

Results reported on 13.8 
kV form-wound hydro generator 
bars made of epoxy resin with 
a high percentage of nanopar- 
ticles of silica, indicated a 
very optimum performance re- 
garding their thermal and me- 
chanical properties. The elec- 
trical performance of such an 
insulation w.r.t. the PD and 
electrical treeing resistance 
was also noted [37], [38]. 
Better resistance to PD and 
electrical treeing implies 
less insulation thickness. 

Before starting an evalua- 
tion of nanocomposite materi- 
als for machine applications, 
let us be clear on a certain 
point: the novel materials 
may offer some new insights 
regarding the endurance of 
the insulation of electrical 
machines, but the condition 
-based maintenance treatment 
is not expected to change 
that dramatically. In other 
words, we are still far from 
new aging models and/or ac- 
celerated laboratory testing 
[40] . In yet other words, sy- 
nergy effects may occur also 
with the new materials and, 
when two or more aging mecha- 
nisms are at work simultane- 
ously, the total degradation 



may not be a single algebraic 
sum of the separate degrada- 
tion outcomes [39], [40]. 

It is rather clear that 
from the two basic components 
that constitute the rotating 
machine insulation, the one 
that is expected to be prone 
for the addition of nanopar- 
ticles, is the epoxy resin. 
Inorganic nitrides and oxides 
(such as, AlN, BN, Si02, ZnO, 
AI 2 O 3 and Ti02 among others) 
may be added in small amounts, 
and if homogeneously disper- 
sed, they may show potential- 
ly better electrical and ther- 
mal properties than the con- 
ventional epoxy resin [41] . 
The need for good dispersion 
of the nanoparticles as well 
as the important role of in- 
terfaces in the nanocomposite 
polymers has been discussed 
elsewhere and there is no 
need for any repetition here 
[42]. Boron Nitride (BN) has 
been used to enhance the di- 
electric properties of the 
groundwall insulation system 
for generators because it has 
a reasonably high resistivity 
( 10 15 ohm. cm) and breakdown 
strength (53 kV/mm) as well 
as a rather small relative 
permittivity (around 4). Such 
inherent properties render BN 
a good nanoparticle material 
to be added to epoxy resin 
[41] . Moreover, the addition 
of BN nanoparticles improved 
the thermal conductivity of 
epoxy resin. In another pub- 



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M.G. DANIKAS, R. SARATHI 



lication, epoxy resin was mi- 
xed with AI 2 O 3 nanoparticles 
[43] . The breakdown strength 
of such a nanocomposite was 
comparable to the breakdown 
strength of conventional epo- 
xy resin but with a lower 
scatter in values. In [43], 
particular attention was paid 
to the fact that nanoparticle 
agglomerations were dependent 
on the method of preparation 
of the nanocomposite. As is 
well known, nanoparticle agglo- 
merations affect the PD, the 
electrical tree propagation 
and the breakdown strength of 
nanocomposites [44] . Zirconia 
nanoparticles added to epoxy 
resin offer an improvement of 
the breakdown strength as 
well as of the thermal and 
dielectric properties. Addi- 
tion of zirconia nanoparti- 
cles to about 5 wt% gives a 
higher breakdown strength com- 
pared to conventional epoxy 
resin [45]. It must, however, 
be noted that in [45], there 
are in certain parts of the 
paper discrepancies between 
the text and the experimental 
data . 

Fillers in insulation sys- 
tems for rotating machines 
are investigated in [46], a 
most thorough review publica- 
tion. Without going into many 
details about the application 
of nanocomposites for machine 
insulation and the role of 
nanoparticles, that paper 
points out several vital as- 



pects of insulation engineer- 
ing, namely, the effect of 
electrical, mechanical and 
thermal stresses, which leads 
to delaminations and/or void 
formation. Nanoparticles are 
deemed to restrain the charge 
transport processes. As a con- 
sequence, nanocomposites ex- 
hibit less space charge for- 
mation than conventional po- 
lymers or their microparticle 
counterparts. The novel ap- 
proach of [46] is that it in- 
sists on a concept for void 
formation that is based on a 
micro-mechanical approach, i. 
e. void formation can be con- 
sidered as a process by which 
the insulating material ac- 
commodates mechanical energy, 
no matter whether this energy 
is purely mechanical, elec- 
tro-mechanical or thermo-me- 
chanical in nature. In the 
case of nanocomposites, crack 
initiation may be considered 
as having a critical nucle- 
ation size. Crack initiation 
sites may well come from na- 
noparticles aggregates, as was 
noted in [47]. In [47], the 
breakdown strength of epoxy 
resin/clay nanocomposites was 
investigated, the clays being 
Cloisite 20A ( C20A) and Cloi- 
site 30B (C30B) with diffe- 
rent levels of loading. It 
was reported that the break- 
down strength depends on the 
level of loading (around 5wt% 
being the optimum) and also 
on the type of nanocomposite 
structure (intercalated nano- 



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composite or exfoliated nano- 
composite), with the exfolia- 
ted type giving the higher 
breakdown strength. Clay C30B 
gave the better results since 
it is more hydrophilic than 
clay C20B and, consequently, 
it has a greater affinity for 
epoxy resin. Epoxy pre-poly- 
mers can more easily interca- 
late into C30B clay galle- 
ries, increasing thus the in- 
terlayer spacing (more de- 
tails on intercalated and ex- 
foliated structures in [48], 
[49]). In yet another paper, 
it was reported that appro- 
priate nanoparticles, if sui- 
tably added, may enhance the 
breakdown time of conventio- 
nal epoxy resin by a factor 
of ten [50] . 

Nanosized particles were 
also discussed in [51], where 
excellent voltage endurance 
results seemed to be very pro- 
mising. Large percentages of 
silica nanoparticles (up to 
25 wt%) were reported for 
making practical coils in VPI 
(vacuum pressure impregna- 
tion) epoxy resin successful- 
ly [52]. The reported percen- 
tage seems to be excessive in 
view of previous publica- 
tions. Nevertheless, for na- 
nocomposite materials in high 
voltage machinery, the prob- 
lems remain much the same as 
with the more traditional in- 
sulations, namely that the 
heat transfer must be satis- 
factory also for the new 



materials, the mechanical 
strength must be high enough 
and the risk from PD must be 
minimized [51] . Recent work 
on mechanical properties sho- 
wed that, with epoxy resin 
and montmorillonite ( MMT ) clay 
mineral, natural frequency of 
vibration and damping factor 
of the said material increase 
by adding up to 5 wt% of nano 
clay [53] . Recent work also 
indicated that epoxy resin 
with 10 wt% Ti02 nanoparti- 
cles improved greatly the ac 
breakdown strength and the 
time to breakdown [54] . 

The percentage of nanopar- 
ticles to be included in a 
base polymer matrix depends 
on the type of nanoparticles 
as well as on the base poly- 
mer. It has been reported, 
for example, that with epoxy 
resin and layered silicate, 
just small amounts of nano- 
particles are enough for the 
improvement of partial dis- 
charge resistance, whereas in 
other publications, it was 
confirmed that only 2 wt% of 
nanoparticles is sufficient 
to improve the partial dis- 
charge resistance of poly- 
amide/layered silicate nano- 
composites [55] -[57]. Small 
amounts of nanoparticles (3 
wt% of Si02 nanoparticles) 
were also reported to improve 
the glass transition tempera- 
ture of epoxy resin in com- 
parison with the neat epoxy 
resin. This is due to the re- 



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M.G. DANIKAS, R. SARATHI 



duction of polymer chains mo- 
bility. On the other hand, in 
the same paper, the resisti- 
vity of epoxy resin with 3 wt 
% of Ti02 nanoparticles was 
lower by one order of magni- 
tude with respect to pure 
epoxy resin [58] . Paper [58] 
is a good example of the de- 
pendence of the nanocomposite 
properties on the nature of 
the added nanoparticles to 
epoxy resin. Further evidence 
as to the effect of the per- 
centage wt% of nanoparticles 
in epoxy resin is offered in 

[59] , where POSS (polyhedral 
oligomeric silsesquioxane) na- 
noparticles were added to the 
base material. Tan<5 measure- 
ments as well as thermo- 
gravimetric analysis showed 
that moderate percentages in 
wt% (between 1% and 4%) of- 
fered the best results. The 
importance of nanoparticle 
percentage and functionaliza- 
tion was also emphasized in 

[60] , where poly (butylene 
te- rephthalate) based poly- 
mers containing alumina nano- 
particles were investigated, 
as alternative to epoxy re- 
sin. It was reported that an 
optimum nanoparticle percent- 
age exists for giving a low- 
ering of the permittivity of 
the resulting nanocomposite 
as well as a lowering of 
tan5. The lowering of the 
aforementioned parameters can 
probably be ascribed to the 
restriction of polymer chain 
movement by nanoparticles due 



to the modified molecular 
structure and chain dynamics, 
which cause a strong surface 
interaction between the nano- 
particle and the polymer ma- 
trix [61] . 

Treeing effects in nano- 
composite epoxy resin propa- 
gate through the base mate- 
rial and do not go through 
the nanoparticles [44], [62]. 
Erosion depth was found to be 
minimal for a combination of 
micro- and nano- particles 

[62] . The desirable result of 
having good thermal conduc- 
tivity and low dielectric con- 
stant is more difficult to 
obtain. In [60], it was shown 
that epoxy resin with h- or 
c- boron nitride nanoparti- 
cles presents higher thermal 
conductivity at the expense 
of a higher dielectric con- 
stant, whereas epoxy resin 
with silica nanoparticles has 
a much lower dielectric con- 
stant but with a far lower 
thermal conductivity. The re- 
ported lower thermal conduc- 
tivity of epoxy resin with 
silica nanoparticles, howe- 
ver, was contradicted in [52], 

[63] . In [52], it was men- 
tioned that nanosized Si02 
particles act as barriers to 
the treeing phenomena and hin- 
der propagation. Moreover, the 
mechanical and thermal pro- 
perties are improved signifi- 
cantly, thus giving a promi- 
sing new insulation system 
with less thickness and bet- 



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ter heat transfer. The dis- 
agreement between [62] and 
[52] may be due to the dif- 
ferent processing methods as 
well as to the different size 
and/or shape of the nanopar- 
ticles . 

Differentiation between 
short-time breakdown and long 
-term failure in nanocompo- 
sites was reported in [64] . 
As the authors pointed out, 
short-term breakdown proper- 
ties depend on the applied 
voltage waveforms as well as 
the bonded region of the 
nanoparticles, whereas for 
long-term aging and failure, 
the transitional region and 
the cohesive energy density 
(CED) of the polymer matrix 
play the dominant role. They 
remarked that the percentage 
weight of nanoparticles to be 
included in a polymer matrix 
depends on the matrix itself, 
the chemical nature of the 
nanoparticles, their func- 
tionalization, their size and 
their bonding to the polymer 
matrix. For example, Ag nano- 
particles of about 20 nm in 
size mixed with epoxy resin 
at about only 0.05 wt% may 
improve the short-term break- 
down strength by about 30% 
w.r.t. the pure epoxy resin. 
Regarding nanoparticle con- 
tent and the polymer matrix, 
it was shown that with 1 wt%, 
epoxy resin nanocomposite has 
a better long-term electrical 
aging resistance than its 



polyethylene counterpart. The 
authors of [64] also remarked 
that PD resistance improves 
as the size of nanoparticles 
decreases because the proba- 
bility of electron collision 
with nanoparticles increases 
leading the electron trans- 
port to become harder. The 
latter statement agrees with 
simulation results presented 
in [42] . 

Rotating machine insula- 
tion will be better served 
with nanomaterials, if such 
materials include nanometric 
layered silica nanoparticles, 
since the latter offer better 
PD resistance and improved 
mechanical properties. As the 
design field nowadays for 
conventional machine insula- 
tion is limited to only about 
3 kV/mm [65], silica nanopar- 
ticles may help to increase 
the design field [66] . Such 
layered silica nanoparticles 
present a barrier behavior, 
rendering them interesting for 
applications . 

Possible Charging Phenome- 
na Below Inception Voltage 

The present paper did not 
deal with either the techni- 
calities of PD measurements 
in rotating machine insula- 
tion or the modeling of life- 
time of such insulation under 
a variety of simultaneous 
stresses (electrical, thermal 
and mechanical) [67] -[69]. 
The literature on such topics 



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M.G. DANIKAS, R. SARATHI 



is very rich to be dealt with 
in the present work. This pa- 
per did not deal either with 
the possibility of charging 
phenomena below the so-called 
inception voltage. Relevant 
work done in the past re- 
vealed that it is possible to 
have sudden failures in insu- 
lation systems (including 
those of rotating machines), 
even though the equipment 
passed the relevant specifi- 
cation tests [30], [70] - [76] . 
More recent research on the 
topic of charging phenomena 
below inception voltage indi- 
cated that in both base epoxy 
resin [77], and in epoxy re- 
sin with Ti02 nanoparticles 
and microparticles, charging 
phenomena were observed [78] . 
It has, however, to be noted 
that in the case of epoxy re- 
sin with nanoparticles and 
microparticles, charging phe- 
nomena below inception were 
rather sporadic. This may be 
due to the bonding strength 
between fillers and matrices, 
the interfiller space or ma- 
trix volume surrounded by 
neighboring fillers and to 
the morphology in the inter- 
filler space [79] . The whole 
subject of possible charging 
effects below the so-called 
inception voltage cannot be 
dealt with in the present pa- 
per. It is, however, a sub- 
ject which unjustly does not 
attract much attention from 
the insulation community. The 
authors intend to come back 



to this subject, possibly 
with another review paper con- 
centrated on this subject on- 
ly. Certainly, for the treat- 
ment of this question, impor- 
tant publications such as 
[80] - [83] , must be taken into 
account . 

Further Developments 

It is understandable that 
there may be alternatives to 
the epoxy resin as insulating 
material for rotating machi- 
nes. Such alternatives may be 
silicone based, resin rich in- 
sulation materials due to 
their thermal stability, fle- 
xibility, anti-vibration and 
very good electrical proper- 
ties. It would be interesting 
to see admixtures of such ma- 
terials with nanoparticles, 
as a further exploration for 
possible applications [84] . 
Furthermore, more fundamental 
research has to be performed 
regarding the combined stres- 
ses on nanocomposite poly- 
mers. Since the various stres- 
ses (electrical, thermal, me- 
chanical etc.) are applied 
not sequentially but combined 
[85] -[88], experimental work 
has to be done in this re- 
spect. In [63], detailed steps 
for future work have been pro- 
posed, such as thermal aging 
and classification tests at 
different temperatures, elec- 
trical aging - voltage en- 
durance tests at various le- 
vels resulting in lifetime 



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curves, multifactor aging as 
well as thermo-mechanical ben- 
ding endurance in parallel 
with electrical stress tests. 
On a more general basis, op- 
timization of nanocomposite 
material fabrication methods, 
a better understanding of in- 
terfaces and possible combi- 
nations of micro- and nano- 
composites may be research 
fields in the future. The 
need for nanocomposites ha- 
ving high breakdown strength, 
low thermal expansion coeffi- 
cient, high thermal conduc- 
tivity, satisfactory long- 
term aging and good with- 
standing capability to multi- 
stressing, will be even more 
pronounced in the coming 
years [89] . The variety of 
nanoparticle sizes and types, 
the variety of polymer matri- 
ces as well as the variety of 
processing methods, leaves us 
with the hope that optimal 
combinations w.r.t. the elec- 
trical, mechanical and ther- 
mal properties, may be found 
for the benefit of the elec- 
trical machines industry. 

Conclusion 

In this paper a review was 
performed for both traditio- 
nal and modern insulating ma- 
terials for rotating machine 
insulation. Traditional insu- 
lation mainly consists of mi- 
ca sheets and epoxy resin. 



with the former being the 
stronger of the two materi- 
als. Electrical trees tend to 
propagate through the epoxy 
resin and have greater diffi- 
culty in breaking through the 
mica sheets. Nanocomposites 
on the other hand offer gene- 
rally better insulating prop- 
erties. The nanoparticles that 
are dispersed in the polymer 
matrix tend to act as ex- 
tremely small barriers, pre- 
venting thus the propagation 
and growth of electrical 
trees. The performance of the 
nanocomposite polymers de- 
pends on a variety of parame- 
ters, such as, for example, 
the type of polymer matrix, 
the type of nanoparticles, 
their functionalization and 
their size. 

Acknowledgments 

One of the authors ( MGD) 
has to thank Miss D. Chri- 
stantoni for the electrical 
tree simulations appearing in 
this paper. The same author 
has also to thank his collea- 
gues at Xi'an Jiaotong Uni- 
versity, State Key Laboratory 
of Electrical Insulation and 
Power Equipment, Xi'an, Peo- 
ple's Republic of China, for 
letting him to carry out ex- 
periments on pure epoxy resin 
and nanocomposite samples and 
to study charging effects at 
and below inception voltage. 



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Previous Publication in FUNKTECHNIKPLUS # JOURNAL 

"Parameters Affecting the Lifetime of Transformer Oil in 
Distribution Transformers: Parameter Monitoring of 50 Trans- 
formers from the Athens Area", Issue 4, Year 1, pp. 53-65 

* About The Authors 

Michael Danikas, Issue 2, Year 1, p. 39 
Ramanujam Sarathi, Issue 2, Year 1, p. 39 



This paper is licensed under a Creative Commons Attribution 4.0 
International License - https : //creativecommons . orq/licenses/by/4 . 0/ 



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TELECOMMUNICATIONS ENGINEERING 



LOGICIEL 



Antenna Radiation Patterns: 

RadPat4W - FLOSS for MS Windows or Wine Linux 

N.I. Yannopoulou, P.E. Zimourtopoulos * 

Antennas Research Group, Austria - Hellas [l, 2] 

Abstract 

This paper briefly highlights the features of the software 
tool [RadPat4W], named after Radiation Patterns for Windows, 
that is based on an alternative exposition of fundamental An- 
tenna Theory. This stand-alone application is compatible with 
the [Wine] environment of Linux and is part of a freeware 
suite, which is under active development for many years. Nev- 
ertheless, the [RadPat4W] source code has been now released 
as FLOSS Free Libre Open Source Software and thus it may be 
freely used, copied, modified or redistributed, individually 
or cooperatively, by the interested user to suit her/his per- 
sonal needs for reliable antenna applications, from the sim- 
plest to the more complex. 



Keywords 

FLOSS, antenna, radiation pattern. Virtual Reality 



Introduction 

Useful software has to work 
exactly as someone wants, so 
the authors' group decided to 
develop its own mini-Suite of 
software tools for antenna 
applications [1] . This pro- 
ject started in the middle of 
90s, when the PC with www ac- 
cess became power enough to 
cover the increased require- 
ments of antenna analysis and 
design, as well as of their 
results presentation and dis- 
tribution. Since then, the 
development of the mini-Suite 
has been orientated towards 



the personal needs of the in- 
dividual user or of the inde- 
pendent member of a small, 
open, loosely connected group, 
like the authors' one, who is 
interested in antenna educa- 
tion, research and engineer- 
ing, i.e., a student, an edu- 
cator, a researcher, a pro- 
fessional engineer or a radio 
amateur. Such a user has 
enough bibliographical resour- 
ces provided by the Open Ac- 
cess movement, but only li- 
mited technical resources for 
construction and measurement. 
The mini-Suite is intended 



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then for the informed user 
who at least can construct an 
experimental thin-wire an- 
tenna model and at most has 
access to a VNA Vector Net- 
work Analyzer to test this 
model - by the way, nowadays, 
the cost of a certified re- 
furbished VNA is just a small 
percentage of its new price. 
For that reason, the mini- 
Suite specifically includes 
the stand-alone application 
[RadPat4W] . 

[RadPat4W] 

The active development of 
this tool attempts to bridge 
the increasing gap of today 
approximate simulation tech- 
niques, which dominate an- 
tenna applications, to clas- 
sic exact analysis methods, 
which concern the demanding 
user who wants to know what 
s/he is really doing with 
these marvellous antenna sim- 
ulators. To achieve this goal 
and facilitate the study of 
antenna application results, 
either approximated or exact, 
[RadPat4W] computes and/or 
plots the antenna geometry, 
its characteristics, as well 
as 2D main-plane cuts of its 
radiation pattern and 3D Vir- 
tual Reality objects for its 
geometry and pattern. Cur- 
rently, the tool uses by de- 
fault: (1) working formulas 
produced by the analysis 
method of the authors' alter- 
native exposition of funda- 



mental Antenna Theory [2] 
that is quickly but rigo- 
rously results in the most 
general complex vector ex- 
pression for the radiation 
pattern of any thin-wire an- 
tenna, and (2) numerical re- 
sults from approximation tech- 
niques based on the Moment 
Method implemented by the two 
antenna simulators [DA] and 
[RichWire], which are inclu- 
ded in the mini-Suite [1] . 
Finally, to support the seri- 
ous user to judge the re- 
sults, the current beta ver- 
sion of [RadPat4W] incorpo- 
rates the superposition on 
the plotted results of scien- 
tific VNA measurements with 
systematic errors first esti- 
mated by the authors in 2008 
[3], a process that is now 
accomplished semi-manually 
using a combination of other 
separate mini-Suite tools. 

Besides [RadPat4W], which 
was always distributed 
through the internet as free- 
ware, other non-commercial sof- 
ware, less related to [Rad- 
Pat4W] and from developers 
with a diverse knowledge of 
Antenna Theory, is distribu- 
ted under various terms of 
use. These ware kinds of the 
free have been exhaustively 
examined by the members of 
the USENET group [alt. comp, 
freeware] with the purpose to 
warn the candidate user about 
the actual content of the 
corresponding licenses. How- 



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ANTENNA RADIATION PATTERNS: RADPAT4W - FLOSS FOR MS WINDOWS OR WINE 



ever, to the best of authors' 
knowledge, it seems that the- 
re is still no completely 
FLOSS for reliable antenna 
applications. Therefore, with 
the aim to further encourage 
the independent user to tweak 
[RadPat4W] according to her/ 
his personal needs or even to 
be involved in this modern, 
most promising, cooperative 
activity of the FLOSS move- 
ment, the authors decided 
lately to release the entire 
source code of [RadPat4W] un- 
der the approved, by the OSI 
Open Source Initiative, MIT 
License . 

The source code, now in 
version 4.4 with help in ver- 
sion 1.0, is developed from 
scratch, without using any 
other code, in MS Visual Ba- 
sic 6 SP6 for 32-bit MS Win- 
dows and the executable, 
which is also compatible with 
the [Wine] environment of Li- 
nux, needs about 8.5 MB of 
free hard disk space for its 
installation. The application 
usability has been multiple 
checked during antenna cour- 
ses and theses elaboration, 
thus its source code is in a 
mature state for a long time 
now although, from time to 
time, new features are added 
to it. The code is available 
for download from authors' 
group website "http://www.ant 
ennas.gr/floss" or GoogleCode 
repository at "http://code.go 
ogle . com/p/rga/" . 



The features of [RadPat4W] 
can be divided according to 
their functionality in two 
groups: (1) pattern computa- 
tion and plotting using work- 
ing formulas from Antenna 
Theory, and (2) pattern plot- 
ting using numerical results 
from antenna simulators. To 
exemplify these features by 
examples, a number of antenna 
education, research and engi- 
neering applications, from 
the simplest to the more com- 
plex, are presented in the 
following . 

Working Formulas 

Fig. 1 shows the software 
application form of [Rad- 
Pat4W] for the three main- 
plane cuts of the E-norma- 
lized radiation pattern of a 
linear, center-fed, standing- 
wave dipole, which is paral- 
lel to z-axis and has a 
length of 2.35A, where the 
length is the only one input 
parameter with values in the 
range [0.001, 10]A. To over- 
come the practical constrains 
of the limited number of 
screen pixels that obscures 
the detailed view of zero-E 
directions, which determine 
the radiation pattern lobes, 
a useful feature has been in- 
troduced in all application 
forms that is the magnifica- 
tion of the pattern up to six 
times. Each magnified diagram 
shows the zero-E directions 
by magenta colored radial li- 



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N.I. YANNOPOULOU, P.E. ZIMOURTOPOULOS 



nes on the screen. The [Max- 
Zero-D] button opens the win- 
dow of Fig. 2 in which the 
computed directions of maxima 
and zeros, as well as, the 



directivity and the maximum 
value of pre-normalized E ra- 
diation pattern, are shown 
[ 2 ]- 



\ Radiation Patterns 




Fig. 1: [One Dipole on z] : A magnified main-plane cut 




Fig. 2: [One Dipole on z] : 
Maximum, zeros and Directivity 



Fig. 3 shows the three 
main-plane cuts of radiation 
pattern for the same dipole 
but in the space direction 
described by the input data 
of its unit directional vec- 
tor: (0.000, 0.707, -0.707). 

The [Zero] button opens the 
window of Fig. 4, where the 
computed directions of zeros 
on the three main-plane cuts, 
as well as on a plane that 
contains the dipole axis, are 
shown . 



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ANTENNA RADIATION PATTERNS: RADPAT4W - FLOSS FOR MS WINDOWS OR WINE 



E 



Radiation Patterns 



One Dipole in Space 



File Radiation Patterns Preferences Window Help 



-Dipole in Space 



L/wl 2.350 





O+x 

o+x 




X 

?, 

1 


0.000 


0.707 


-0.707 


0 Other 


□ + 0 - 







r Pixels -| 
0 10 2 
0 3 0 4 



theta 


xOy 


yOz 


zOx 


0 




0.029 


_ 


1 




0.042 




2 




0.115 




3 




0.190 




4 




0.265 




5 




0.340 




6 




0.414 





xOy 



yOz 





Fig. 3: [One Dipole in Space]: Three different main-plane cuts 




Fig. 4: [One Dipole in Space]: Zero pattern directions 



Fig. 5 shows the input 
data for a uniform linear ar- 
ray of exactly parallel lin- 
ear standing-wave dipoles, in 
two frames for the generator 
dipole with complex vector 
pattern G and the array of 
isotropic sources with com- 
plex number pattern A, re- 
spectively. The first frame 



defines the length and the 
direction of the generator or 
reference dipole. The second 
frame defines the geometrical 
and electrical input data for 
the array: the number of iso- 
tropic point sources, their 
constant phase difference in 
degrees, their constant equi- 
distance per wavelength, and 



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N.I. YANNOPOULOU, P.E. ZIMOURTOPOULOS 



the unit directional vector 
of array axis. The shown val- 
ues are for an array of 3 
dipoles, 2A each, in the di- 
rection of +y axis, with 
phase difference of -144°, 
0.4A apart, on the array axis 
direction of +x. The [Show 
Graphics] button opens the 
window of Fig. 6, in which 
the dipole array complex vec- 
tor pattern E = AG, i.e., the 
Principle of Radiation Pat- 
terns Multiplication, is shown 
in absolute 3D form: the nor- 
malized norm pattern ||E|| 
results as product of the 
normalized absolute pattern 
| A | by the normalized norm 
pattern ||G|| and by a non- 
shown constant spherical pat- 
tern | A | max | | G | | max / | | E | | max > 1 
[2] . In the [Directivity] 
frame of the window, the di- 
rectivities of the array Da, 



of the generator Dg, and of 
the dipole array D are shown. 
The [Max-Zero of Array Fac- 
tor] button opens the window 
of Fig. 7, in which the di- 
rections of zero-A and |A| max 
and the values of |A| max , || 



and 



are shown. 



The buttons [A-3D], [G-3D] 

and [E-3D] produce the re- 
spective 3D Virtual Reality 
radiation patterns, which are 
shown in Fig. 8 as three 
screen captures of the free 
Platinum Worldview VRML vie- 
wer plug-in for MS Internet 
Explorer. By the way, the 
contemporary free VRML Cor- 
tona viewer is available for 
a number of other web brow- 
sers too, under MS Windows, 
while under Linux the most 
appropriate add-on for ice- 
weasel (Mozilla Firefox) is 
the FreeWRL VRML viewer. 




Fig. 5: [Array Data]: Uniform Linear Array input 



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Fig. 6: [Array Graphics]: 9 main-plane pattern cuts, 2 zeros 



| Max and Zero Values of Array Factor - Max Values of Patterns E 




* Zero | Sd 




t Max | 






1 80.41 




1 0.00 






2 131.81 









- Max of Patterns — 
Emax2D= 6.69 


Amax2D = 3.00 


Gmax2D = 2.34 


Emax 3D = 6.67 


Am ax 3D = 3.00 


Gmax3D = 2.34 



Back | 



Fig. 7: [Max-Zero of Array Factor]: Computed results 




Fig. 8: Virtual 3D Principle of Radiation Pattern 
Multiplication 



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A/. I. YANNOPOULOU, P.E. ZIMOURTOPOULOS 



Antenna Simulators 

The second group of [Rad- 
Pat4W] features concerns its 
ability to plot antenna geo- 
metry and patterns from the 
clear text data files such 
those of the two antenna si- 
mulators of the mini-Suite: 
[DA] and [RichWire] . The sour- 
ce code of [DA], now in ver- 
sion 1.0.8, has been written 
in Compaq Visual Fortran 6.1 
as Quick-Win 32-bit applica- 
tion for MS Windows, and the 
executable, which is also com- 
patible with the [Wine] envi- 
ronment of Linux, can be eas- 
ily installed on a PC with 
free hard disk space of only 
about -500 KB. 

In essence, this applica- 
tion is a restricted varia- 
tion of [RichWire], which is 
a fully analyzed, corrected 
and redeveloped edition of 
the original Moment Method 
thin-wire computer program by 
J . H . Richmond, available in 
the public domain by NASA 
since 2005 [4] . [DA] is used 
for antenna simulation by 
half-wave dipoles, with just 
one active. The program re- 
quires an input data file to 
derive three output data fi- 
les. All these data files are 
used by [RadPat4W] . In Fig. 
9, the simplest data for only 
one dipole in space are 
shown. [RichWire] data files 
are similar. The usability of 



both antenna simulators has 
been also multiple checked. 
The simulators are available 
as freeware from the men- 
tioned repositories. 

In Fig. 10, the [RadPat4W] 
engineering application for a 
commercial VHF Yagi-Uda an- 
tenna is shown. The [Antenna] 
button reads the antenna geo- 
metry [RichWire] data input 
file. The [geo.wrl] button 
produces the 3D Virtual Rea- 
lity antenna geometry and si- 
multaneously opens the [GL Vie- 
wer for Mathematica] for an 
immediate view [5]. In Fig. 
11, the drawn results produ- 
ced by [RadPat4W] are shown 
for an educational applica- 
tion of a flat airplane mo- 
deled with non-overlapping A/2 
dipoles in [DA] [6]. Fig. 12 
illustrates the drawn results 
produced by the currently be- 
ta version of [RadPat4W] for 
a research application of a 
constructed Hentenna model, 
simulation designed with [Rich 
-Wire] and measured with a 
VNA system [7] . 

[RadPat4W] Development Plans 

Scheduled expansions of 
[RadPat4W] include the fol- 
lowing facilities, which are 
already available in other 
mini-Suite tools: (1) choice 
of other plane- or conical- 
cuts, (2) key-in of any exact 
analysis working formula E(0, 



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cp), (3) selection of the Z,- , 
0-, and cp- plotting step, (4) 
automation of fine Cartesian 
pattern plotting, (5) super- 
position of VNA measurements 
on 3D Virtual Reality pat- 
terns, such as that in the 
left part of Fig. 13 [8], and 
(6) superposition of VNA mea- 
surements with their diffe- 
rential error cloud [3] on 2D 



plots, such that in the right 
part of Fig . 13 [9] . 

Any other expansion of the 
freely available code is of 
course welcomed. In authors' 
group, there are no plans in 
the near future to upgrade 
the mini-Suite to an inte- 
grated environment for its 
tools . 




Fig. 9: [Da]: Input and output data for the simplest case 



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N.I. YANNOPOULOU, P.E. ZIMOURTOPOULOS 



Radiation Patterns - [Radiation Pattern By Data] 



GL Viewer for Mathem.. 



A File Badiation Pattern [-jggfl 




i i 


© 


o 


1 y° z 


HzO 


0.189 




0.194 




0.199 




0.205 




0.211 




0.218 




0.225 




yoz 







Fig. 10: [RichWire] : A commercial VHF Yagi-Uda antenna 




Fig. 11: [RadPat4W] : Results for a flat airplane model 



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Fig. 12: [RadPat4W] : Design, Construction and Measurement 




Fig. 13: 3D VNA measurements and their 2D error cloud 



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A/. I. YANNOPOULOU, P.E. ZIMOURTOPOULOS 



References * 

[1] Yannopoulou N., Zimourtopoulos P., "Mini Suite of An- 
tenna Tools, Educational Laboratories, Antennas Research 
Group, 2006, 

"www. antennas . g r /ant soft /minis uiteof tools/" 

[2] Zimourtopoulos P., "Atenna Notes 1999-, Antenna Design 
Notes 2000-, "www.antennas.gr/antennanotes/" (in Greek) 

[3] Yannopoulou N., Zimourtopoulos P., "S-Parameter Uncer- 
tainties in Network Analyzer Measurements with Applica- 
tion to Antenna Patterns", Radioengineering, Vol. 17, No. 
1, April 2008, pp. 1-8 

"www. radioeng . cz/f ulltexts/2008/08_01_01_08 . pdf" 

[4] Richmond J . H . , "Computer program for thin-wire structu- 
res in a homogeneous conducting medium". Publication 
Year: 1974, NTRS-Report/Patent Number: NASA-CR-2399, ESL- 
2902-12, DocumentID: 19740020595, "http://ntrs.nasa.gov/" 

[5] Kuska J.-P., "MathGL3d: An Interactive OpenGL Based Vie- 
wer for Mathematica ' s 3D Graphics, Version 2.2, 

"http : //library .wolf ram . com/inf ocen ter /Mat hSource/2986/" 

[6] Johnson R.C., "Antenna Engineering Handbook", 3rd Edi- 
tion, McGraw-Hill, 1993, ch. 37, p. 11 

[7] Babli E., "Hentenna", Diploma Thesis #31, ARG-Antennas 
Research Group, DUTh, 2004, ch. 6 (in Greek) 

[8] Yannopoulou N., "Development of a broadband antenna for 
3rd generation mobile telephony systems", MEng Thesis, 
ARG-Antennas Research Group, DUTh, 2003, ch. 6, p . 24 (in 
Greek) 

[9] Yannopoulou N., "Study of monopole antennas over a multi 
-frequency decoupling cylinder", PhD Thesis, ARG-Anten- 
nas Research Group, DUTh, 2008, ch. 5 (in Greek) 

*Active Links: 04.08.2014 - Inactive Links : FTP#J Link 

Updates: "http://updates.ftpj .otoiser.org/" 

Preprint Versions 

"A FLOSS Tool for Antenna Radiation Patterns" 

Nikolitsa Yannopoulou, Petros Zimourtopoulos 
"http : //arxiv . org/abs/1002 . 3072" 

Proceedings of 15th Conference on Microwave Techniques, 
COMITE 2010, Brno, Czech Republic, pp. 59-62 



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Follow-Up Research Paper 

Not until now 



Previous Publication in FUNKTECHNIKPLUS # JOURNAL 

"Self -Standing End-Fed Geometrically Uniform Linear Arrays: 
Analysis, Design, Construction, Measurements and FLOSS", 
Issue 4, Year 1, pp. 43-52 



* About The 

Nikolitsa Yannopoulou , Issue 
Petros Zimourtopoulos , Issue 



Authors 

1, Year 
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1 , 

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p. 15 
p. 15 



This paper is licensed under a Creative Commons Attribution 4.0 
International License - https : //creativecommons . orq/licenses/by/4 . 0/ 



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FRONT COVER VIGNETTE 

A faded synthesis of an anthemion rooted in a meandros 

The thirteen-leaf is a symbol for a life tree leaf. 

"Herakles and Kerberos", ca. 530-500 BC, 
by Paseas, the Kerberos Painter, 
Museum of Fine Arts, Boston. 

www. mfa . org/collect ion s/object /plate -153852 

The simple meandros is a symbol for eternal immortality. 

"Warrior with a phiale", ca. 480-460 BC, 

by Berliner Maler, 

Museo Archeologico Regionale "Antonio Salinas" di Palermo, 
commons .wikimedia . org/wiki/File :Warrior_MAR_Palermo_NI2134. j pg 



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